This invention relates to detector circuits and in particular to dynamic sense-refresh detector amplifiers useful in dynamic random access memory (RAM) systems.
A basic detector for such use is essentially a flip-flop circuit in which current alternates from one leg to the other as a function of an input signal. Each leg contains an MOS load transistor in series with an MOS switching transistor. The gate of each switching transistor is cross coupled to the drain of the other switching transistor. A dc voltage supply is applied to the common drains of the load transistors and an input signal is coupled to one of the gates of the switching transistors. One of the major problems of this detector is that power dissipation is relatively high since there is essentially always dc current flow.
The use of the basic MOS detector flip-flop with a pulsed voltage power supply reduces power dissipation. Ideally power should be turned off just after the proper output state is achieved. One difficulty is that a reasonable time span must be provided after the output is supposed to have reached the correct level in order to insure that in fact the correct level is achieved. This is wasteful of power.
Alternatively detector circuits providing two sets of cross coupled MOS transistors have been utilized to automatically limit power dissipation by opening all dc paths at least by the time output signals reach the appropriate levels. One of the problems associated with this kind of detector is that the complexity and the dual cross coupling requires a considerable amount of silicon area for implementation thereof.
It would be desirable to have a sense-refresh detector amplifier which operates dynamically, has relatively low power dissipation, and requires a relatively modest amount of silicon area for implementation thereof.